JP2000031464A - Electron element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electronic element, particularly single-electronic element, of which the tunnel resistance and the junction capacitance can be designed independently without limiting materials and which has directivity of a tunnel. SOLUTION: An electron element comprises at least a pair of electrodes 1 and 2, a tunnel formed at the electrodes 1 and 2, means for providing the dependence of distribution for wave functions at the electrodes 1 and 2 on energy, and the tunnel resistance of the tunnel junction changes, depending on the voltage applied to the electrodes. This allows the capacitance component and the tunnel component of the electrodes 1 and 2 to be set independently and the directivity of the tunnel junction to be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic device,
More specifically, the present invention relates to an electronic device and a single-electron device using a tunnel junction.

[0002]

2. Description of the Related Art Hitherto, electronic devices utilizing the tunnel effect by applying a thin film forming technique have been proposed and manufactured, and the tunnel effect is a physical phenomenon that is important for the operation principle of the electronic device.

In recent years, a tunnel junction having a small capacitance has been trial-produced by making full use of microfabrication technology, and research on single-electron tunneling that occurs in such a tunnel junction has been actively conducted. The use of the single-electron tunneling phenomenon makes it possible to realize an electronic device that operates at a very high speed and consumes very little power as compared with a conventional macro electronic device. To realize this, trial production research of single-electron devices is being conducted everywhere.

The principle of single electron tunneling is as follows. In a tunnel junction having a very small capacitance, a change in charging energy due to the transfer of one electron (tunneling through the junction) is caused by a temperature fluctuation kT.
(T: absolute temperature, k: Boltzmann's constant). In such a case, even if it is a tunneling of one electron, a tunnel phenomenon in which energy is increased does not occur. Such a phenomenon,
It is called Coulomb blockade and is the basic concept of single electron tunneling.

There are the following problems with respect to such a tunnel phenomenon.

The conventional tunnel junction has no directionality with respect to the direction of electron tunneling. Therefore, in order to suppress tunneling of electrons from a direction other than a predetermined direction, that is, a current flowing in the reverse direction is suppressed. Therefore, an external element such as a rectifying element is required. Furthermore, the directionality of the electronic element depends on the direction in which the bias voltage is supplied, the combination of the values of the junction capacitance, and the like, and requires a complicated circuit configuration.

In particular, in order to apply a tunnel junction to a single-electron element to operate stably at room temperature, the charging energy e ² / 2C per electron is reduced by the thermal energy k at room temperature.
Must be larger than T. That is, it is necessary to reduce the junction capacitance C. Generally, the junction capacitance of a tunnel junction satisfying such conditions is 10 ⁻¹⁸ F or less. According to electromagnetism, the capacitance C of a capacitor consisting of parallel plate electrodes with an electrode area S and a distance d between the electrodes is: C = εS / d. Therefore, when the junction area is kept constant, it is necessary to increase the distance d between the electrodes in order to reduce the junction capacitance. However, the tunnel probability between the electrodes, although strictly affected by the shape and structure of the electrodes, is proportional to: exp (-d) for the distance d between the electrodes. Therefore, when the distance d between the electrodes is increased,
Tunnel probability decreases and tunnel resistance increases. That is, when the operating temperature T is increased, it is necessary to increase the distance d between the electrodes for stable operation, and as a result, the tunnel resistance increases and the operating speed decreases. That is, it is necessary to balance the operating temperature and the operating speed, and the two cannot be determined independently.

Further, even in a region where the electron tunneling is prohibited by the Coulomb blockade and the current is interrupted (Coulomb blockade region), a leakage current is observed due to the influence of multiple tunneling (co-tunneling). . It has been found that leakage current due to multiple tunneling can be reduced by increasing the resistance of the tunnel junction or increasing the number of junctions. However, the method of increasing the resistance of the tunnel junction causes a decrease in operating speed. Therefore, the method of increasing the number of junctions is mainly used, but this method requires a more complicated circuit configuration using a multi-tunnel-junction structure such as a turn-style type. I do.

An example of a tunnel junction which has solved the above-mentioned problem is disclosed in Japanese Patent Application Laid-Open No. Hei 8-264752. This electronic device includes a tunnel junction having a composite barrier structure as shown in FIG. According to such a structure, different barrier thicknesses are exhibited according to the potential difference between the barriers, and thus different tunnel resistances are exhibited, so that the tunnel resistance can be changed as a function of the potential difference. Therefore, as shown in FIG. 13A, when electrons are tunneled in the direction from A to B, different tunnel resistances are provided according to different voltage states. In this case, the junction capacitance of the tunnel junction does not change with respect to electrons passing through any of the paths from T _{1 to} T _n in FIG. On the other hand, as shown in FIG. 13B, when electrons tunnel from B to A, the tunnel resistance shows a constant value independent of the voltage state. Furthermore, if the tunnel resistance when electrons tunnel from A to B is set to a value smaller than the tunnel resistance when electrons tunnel from B to A, the electrons tunnel. In this case, it is possible to give directionality to the tunnel resistance. In this way, it is possible to independently design the tunnel resistance and the junction capacitance, and at the same time, to provide directionality in the electron tunnel direction. Therefore, when the above-mentioned tunnel junction is applied to an electronic element, particularly a single-electron element, it is possible to determine the operating temperature and the operating speed independently and to suppress the leakage current, and furthermore, the element itself has a directivity. Can be provided.

[0010]

In JP-A-8-264752, the above problem is solved by forming a tunnel junction in which barriers having different heights are combined. However, in order to actually form such an electronic element, it is necessary to use a material whose barrier height can be controlled. Examples of such a material include a mixed crystal compound semiconductor such as aluminum gallium arsenide. For example, in the case of aluminum gallium arsenide, the height of the barrier can be controlled by the composition ratio of aluminum and gallium. However, most of the materials actually used in the semiconductor industry today are silicon-based, such as silicon nitride, silicon oxide, and metals. These material systems do not have a suitable mixed crystal system that can control the barrier height. Therefore, there is a problem that the structure described in the above-mentioned document cannot be formed depending on the material system used.

An object of the present invention is to provide an electronic device having a tunnel directionality, in which a tunnel resistance and a junction capacitance can be independently designed without being limited by the above-described material system, and in particular, a tunnel direction. It is to provide a single-electron element.

[0012]

An electronic device according to the present invention includes at least a pair of electrodes, a tunnel junction formed at the electrodes, and means for imparting energy dependence to the distribution of a wave function at the electrodes. An electronic element, wherein a capacitance component and a tunnel component of the electrode are independently set by changing a tunnel resistance of the tunnel junction depending on a voltage applied to the electrode; It has directionality.

[0013] In a preferred embodiment, the means for imparting energy dependence to the distribution of the wave function includes one or more quantum devices disposed in proximity to one of the pair of electrodes. Structure.

In a preferred embodiment, the means for imparting energy dependence to the distribution of the wave function includes one or more quantum devices arranged in contact with one of the pair of electrodes. Structure.

[0015] In a preferred embodiment, the electronic element is a single electronic element.

In a preferred embodiment, at least one pair of the tunnel junctions is provided, a Coulomb island is provided between the pair of tunnel junctions, and the series connection is such that the directions of the pair of tunnel junctions are opposite to each other. To suppress multiple tunneling.

Hereinafter, the operation of the present invention will be described.

The electronic device of the present invention includes at least a pair of electrodes and a tunnel junction formed on the electrodes. Generally, according to quantum mechanics, if the wave functions of a pair of electrodes 1 and 2 are Ψ1 (z) and Ψ2 (z), respectively, and the potential of an insulator between the electrodes is T (z), the z-direction of the tunneling phenomenon The tunnel current I is:

(Equation 1) Satisfies the relationship. Here, it is considered that the wave function in the high-energy state is distributed close to the remaining electrodes in one electrode, and the wave function in the low-energy state is distributed near the electrodes themselves. If the energy distribution is given to such a distribution of the wave function, it becomes possible to give the tunnel current an energy dependency, and thus it is possible to give the tunnel resistance an energy dependency. The electronic element of the present invention includes means for giving such a wave function distribution energy dependency. When the energy distribution is given to the distribution of the wave function, the degree of seepage of the wave function depends on the energy. Therefore, the energy dependence can be given to the tunnel resistance. Therefore, since the tunnel resistance can be controlled by adjusting the above-described means, the tunnel resistance can be set independently of the capacitance of the tunnel junction. Furthermore, such electronic devices are not limited by the material system.

More specifically, in a preferred embodiment of the present invention, a quantum structure 3 is arranged close to the electrode 2, as shown in FIG. For this reason, the wave function of the quantum level E ₀ due to the quantum confinement effect of the quantum structure 3 is combined with the wave function of the same energy of the electrode 2, and the combined wave function is as shown in FIG. And distributed over the electrode 2. Therefore, the distribution of the wave function can be changed by the quantum structure 3, and the quantum level E ₀ is changed by adjusting the structure of the quantum structure 3 with respect to the electrodes 1 and 2.
Since the distribution of the combined wave function can be changed, the distribution of the wave function can have energy dependency. Figure 5 (a), in the condition where the voltage V as the Fermi energy is E ₀ greater than the Fermi energy E _F of the electrode 2 of the electrode 1 is applied, between the electrodes 1 and the quantum structure 3 The distance determines the tunnel resistance. Under other voltage application conditions, the tunnel resistance is determined by the distance between the electrode 1 and the electrode 2. That is, such a tunnel junction has a directionality from the electrode 1 to the electrode 2 under the condition where the voltage V is applied, and has a tunnel resistance lower than the tunnel resistance under other conditions. Therefore, it is possible to change the tunnel resistance according to the conditions (direction and magnitude) of the voltage applied to the electrode. On the other hand, the junction capacitance of this tunnel junction is based on a mechanism in which electrons reaching the electrode 2 from the electrode 1 through the quantum structure 3 are relaxed by a cooling mechanism due to lattice vibration or the like.
Can be set at a distance between As described above, only by providing the quantum structure 3, it becomes possible to change the tunnel resistance and to give directionality to the electron tunneling direction without changing the junction capacitance. Furthermore, such electronic devices are not limited by the material system.

The above-described electronic device can be similarly applied to a single electronic device. In a preferred embodiment of the present invention, the single-electron element of the present invention includes a pair of tunnel junctions as described above, and is connected in series so that the directions are opposite to each other. On the other hand, the resistance of the tunnel junction in the Coulomb blockade region can be made larger than the resistance in the operation region. As a result, the single electron device of the present invention may further have a function of suppressing multiple tunneling.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described with reference to the drawings, but the present invention is not limited to these embodiments.

(Embodiment 1) FIG. 1 is a schematic view illustrating the structure of a tunnel junction according to the present invention. This electronic device is composed of electrodes 1 and 2 and a quantum structure 3 arranged in the vicinity of the electrode 2. Regarding these positional relationships, the distance between the electrode 1 and the quantum structure 3 and the distance between the quantum structure 3 and the electrode 2 are set so as to cause a tunnel effect and a coupling of a wave function, respectively. . Tunneling and wave function coupling phenomena occur, for example, at less than about several thousand angstroms, and at about several angstroms to several tens of angstroms, respectively. Here, these values can vary depending on the material and structure of the electronic element, and are not limited to these as long as tunneling and coupling of the wave function can occur.

The quantum structure 3 has a quantum level E _{0 due} to the quantum confinement effect. This quantum structure 3 can be of any suitable size, for example, less than about a few hundred angstroms. As described above, the distance is not limited to this value as long as the quantum confinement effect can occur in a larger structure depending on the material and the structure.

The wave function of the quantum structure 3 is combined with the wave function of the electrode 2 by being disposed in the vicinity of the electrode 2,
As shown in FIG. 2A, an energy level is formed over the electrode 2 and the quantum structure 3.

Hereinafter, a case where the electrodes 1 and 2 and the quantum structure 3 are all made of metal will be described with reference to an energy band diagram. The electrodes 1 and 2 and the quantum structure 3
In the case where any one of the above is a semiconductor, the same explanation can be given as below by merely setting the Fermi surface to the Fermi level and providing a forbidden band in which electrons cannot exist.

Furthermore, when the wave functions are combined to form a new level as described above, an energy shift occurs due to the overlapping interaction. Here, the energy structure is combined with the quantum structure 3 after the coupling and the interaction is incorporated. The description will be made below by replacing the energy level across the electrode 2 with E ₀ .

[0027] R _h 13 in FIG. 2 (b), the tunnel resistance between the electrode 1 and the quantum structure 3, R _l 12 represents the tunneling resistance between the electrodes 1 and 2.

[0028] If the voltage V between the electrodes 1 and 2 is not applied, as an equivalent circuit, parallel circuit of the tunnel resistance R _l 12 as in FIG. 2 (c), the junction capacitance C12 between the electrodes 1 and 2 Is shown.

The case where the voltage V is sequentially applied to this tunnel junction from the state where no voltage is applied in FIG. 2A will be considered below.

As shown in FIG. 3A, the energy difference eV due to the applied voltage V is equal to the quantum level E ₀ in the quantum structure 3.
If less than, as in the case of FIG. 2, the resistance to electrons passing through the junction is R _l 12, further junction capacitance remains C12. On the other hand, as shown in FIG. 4A, when a voltage −V having the same magnitude is applied in the opposite direction to that of FIG. 3A, the tunnel resistance and the junction capacitance do not change.

Next, as shown in FIG. 5A, when the energy difference eV between the electrodes 1 and 2 due to the applied voltage V is larger than the quantum level E ₀ in the quantum structure 3, electrons are first applied to the electrode 1 , Tunneling to the quantum structure 3, and further move to the electrode 2 to which the wave function is coupled, and is instantaneously relaxed. Therefore, the tunnel resistance R for electrons is R _h13 ,
The junction capacitance remains at C12. Therefore, it is possible to change the tunnel resistance without changing the junction capacitance. On the other hand, as shown in FIG. 6A, when the same voltage -V is applied in the opposite direction to that of FIG. 5A, electrons cannot tunnel beyond the level in the quantum structure 3, and The tunnel resistance is _Rl12 . As described above, the tunnel resistance of the tunnel junction formed in the electronic device of the present invention depends on the magnitude of the applied voltage and the application direction (that is, the directionality) without being limited by the material.

(Embodiment 2) In another embodiment of the present invention, the distance between the electrode 1 and the quantum structure 3 is such that a tunnel effect occurs, and the distance between the quantum structure 3 and the electrode 2 is The distance is such that there is no coupling of the wave functions, but such that a tunnel effect occurs. In the present embodiment, as shown in FIG. 7, when the energy difference eV due to the applied voltage V is larger than E ₀ , the tunnel resistance R _h13 between the electrode 1 and the quantum structure 3 and the energy difference due to the applied voltage V eV is E ₀
If smaller, not only the tunnel resistance R _l 12, further when the energy difference eV is greater than E ₀ by the applied voltage V, must consider the tunneling resistance R _h 32 between the quantum structure 3 and the electrode 2 There is.

As in FIGS. 3A and 4A, when the energy difference eV due to the applied voltage V is smaller than the quantum level E ₀ in the quantum structure 3, the same principle as in the first embodiment is applied. , joining the whole of the tunnel resistance R _l 12, the junction capacitance becomes C12.

[0034] Similarly Figure 5 as (a), when the energy difference eV due to the applied voltage V is greater than the quantum level E ₀ in the quantum structure 3, tunneling resistance R of the whole junction, R _h 13+
R _h 32. Also in this embodiment, has a nonlinearity of the tunnel current is proportional to exp (-d) to the bonding distance d, the distribution of the wave function at a lower energy than the energy E ₀ by the quantum structure 3 from different, in this case the tunnel resistance _{R (= R h 13 + R} h 3
2) it is smaller than R _l 12, the tunnel resistance is reduced. On the other hand, as in FIG. 6A, when the same voltage −V is applied in the opposite direction to FIG. 5A, the tunnel resistance of the entire junction becomes R _l 1
2. The junction capacitance becomes C12, and electrons cannot tunnel beyond the level in the quantum structure 3.

Accordingly, the tunnel resistance of the tunnel junction according to the present embodiment is also not limited by the material, and
It depends on the magnitude of the applied voltage and the direction of application.

(Embodiment 3) Furthermore, the quantum structure 3 is
It may be arranged more proximally than. In the present embodiment,
As shown in FIG. 8A, the distance between the electrode 1 and the quantum structure 3 is the distance at which a tunnel junction occurs, and the quantum structure 3 and the electrode 2 are joined. Also in this case, FIG.
If the distribution of the wave function has energy dependence as shown in (c), it operates on the same principle as in the first embodiment. Therefore, the tunnel resistance of such an electronic element depends on the magnitude and direction of the applied voltage without being limited by the material, and the junction capacitance and the tunnel resistance can be designed independently.

In the first to third embodiments, only E ₀ is considered as the quantum level due to the quantum confinement effect in the quantum structure 3, but a plurality of quantum levels may exist. At this time, it may be put to the E ₀ those of the lowest energy among them. Further, when the distribution of the wave functions of a plurality of quantum levels is different, by the same principle as in the above embodiment,
It becomes possible to control a plurality of tunnel resistances according to a voltage application condition.

Furthermore, if the purpose of imparting energy dependence to the tunnel resistance is achieved by imparting energy dependence to the distribution of the wave function, the shape of the quantum structure can be any suitable shape, For example, boxes, pillars,
Examples include prisms, cylinders, spheres, and composite structures combining them. Further, the number of quantum structures between the electrodes forming the tunnel junction is not limited to one, but may be plural.

In the above description, the electrode has been described as a bulk having a continuous energy level. However, if the purpose of imparting energy dependence to the distribution of the wave function of the electrode is achieved, the electrode is also discrete. It may be a quantum structure having various levels.

If the shape and material of the electronic element can be controlled so that the distribution of the wave function can have energy dependence, the quantum structure need not be formed between the electrodes. Further, the material forming the tunnel junction in the present invention may be the same or different for the two electrodes and the quantum structure, and any appropriate material is used.

(Embodiment 4) Hereinafter, application of the above-described tunnel junction to a single-electron device will be described. Here, the above-mentioned tunnel junction and its directionality are represented by symbols shown in FIG. The two joined squares represent a tunnel junction, and the arrows in the rectangle represent the directionality of the tunnel junction described in the above embodiment. The right-pointing arrow in the square in FIG. 9 corresponds to the directionality of the tunnel of the tunnel junction formed in the electronic device of the present invention shown in FIGS.

FIG. 10A shows a single electron device according to another embodiment of the present invention.

This single-electron element has a structure in which the two tunnel junctions are connected in series so that the directions of the tunnels coincide with each other, and a Coulomb island is provided in a region between the two tunnel junctions. Coulomb Island has a gate capacitance C as shown in FIG.
_It is connected to an external circuit via _g .

This single-electron element is similar to the above-described embodiment.
10A, the direction of electrons in the direction from A to B (forward direction) in FIG.
For propagation, depending on the magnitude of the voltage applied to the junction
And R _lOr R_hThe resistance value can be any of Only
And the propagation of electrons from B to A (reverse direction)
Means that the resistance value is always R_lIt is. Therefore, power from the forward direction
Set to propagate electrons and not propagate electrons from the opposite direction
Can selectively control the propagation of electrons.
You. That is, the single-electron device according to the present invention has directionality.
ing.

Further, in the single electron device of FIG.
If the applied voltage V is set so that eV> E ₀ so that the tunneling electrons always have a resistance value of R _h, the tunnel resistance value can be reduced without changing the junction capacitance value. It is. As a result, the operation speed can be improved as compared with a conventional single electron device having the same junction capacitance.

(Embodiment 5) Referring to FIG. 11, the operation principle of a multi-tunneling suppressing single-electron device having a tunnel junction in another embodiment of the present invention will be described. FIG.
FIG. 2 is a schematic diagram illustrating a normal single-electron element having no quantum structure, for comparison with a multi-tunneling suppressing single-electron element.

In this multi-tunneling suppressing single-electron element, the two tunnel junctions are connected in series so that the directions of the tunnels are opposite to each other, and a Coulomb island is formed in a region between the two tunnel junctions. It has a provided structure.

The operating region, that is, the applied voltage V (eV = eV =
When (E ₀ ) is applied, as shown in FIG. 11A, electrons pass through the junction C2 with the tunnel resistance R _h and pass through the junction C1 with the tunnel resistance R ₁ . Here, the tunnel resistance R _l
The definitions of R _h and R _h are the same as those shown in FIG. 10A, and satisfy the relationship of R _l > R _h as described in the above embodiment. As shown in FIG. 14 (a), a single electronic device using the conventional tunnel junction passes through both of the bonding C1 and junction C2 in tunnel resistance R _h.

As shown in FIGS. 11 (b) and 14 (b), the number of electrons in the Coulomb blockade region, that is, the Coulomb island, is increased by one from N to N + 1. Since the level indicated by N + 1 is higher than that in state A, a normal tunnel phenomenon occurs.
Even in the case where (indicated by a broken line arrow in each drawing) is prohibited, if the energy of the state B is lower than that of the state A, tunneling of electrons from the state A to the state B occurs (see each drawing). Is indicated by a solid arrow). Such a phenomenon is called multiple tunneling.

Here, the energy levels N and N + in Coulomb island shown in FIGS.
Numeral 1 indicates the energy not due to the quantum confinement effect but taking into account the electrostatic energy due to the junction capacitance when N and N + 1 electrons are present on the Coulomb island, respectively.

In the Coulomb blockade region, electrons cannot tunnel into the Coulomb island by ordinary tunneling, but do tunnel into the Coulomb island by multiple tunneling. The tunneled electrons do not form a steady state in Coulomb island. Therefore, this electron can take any energy state in Coulomb island. Therefore, since the tunnel resistance of a normal tunnel junction as shown in FIG. 14 does not change depending on the energy state of electrons, the tunnel resistance that electrons undergoing multiple tunneling during the Coulomb blockade region (FIG. 14B) is
In the operation region (FIG. 14A), the resistance is equal to the resistance of the tunneling electrons. Therefore, an electronic device having a normal tunnel junction cannot suppress multiple tunneling.

However, in the multi-tunneling suppressing single-electron device according to the present invention, as shown in FIG. 11B, the tunnel resistance of the junction C1 is always R regardless of the energy state of the electrons in the Coulomb island. _l . Moreover, setting the tunnel resistance of the junction C2, as when Coulomb blockade area set to be (FIG. 11 (b)) in R _l, in the operation region (FIG. 11 (a)), the R _h are doing. Therefore, the resistance received by the multi-tunneling electron in the Coulomb blockade region is R _l + R _l ,
The resistance becomes larger than the resistance R _l + R _h that the tunneling electrons receive in the operation region. As a result, the single-electron element of the present embodiment has a function of suppressing multiple tunneling, and becomes a multiple-tunneling suppressing single-electron element.

The preferred embodiment of the present invention has been described above. Next, a method of forming a tunnel junction as described above will be described using an SOI substrate as an example.

FIGS. 12A to 12C are perspective views for explaining a method of forming an electronic device according to the present invention. The electronic device 100 shown in FIG. 12C includes a silicon substrate 11, a buried oxide film 12, electrodes 1 and 2 made of a silicon layer, and a quantum structure 3 made of a silicon layer.
2 and an SiO ₂ film 15 on the quantum structure 3.

Silicon substrate 11 and buried oxide film 12
An electron beam resist made of PMMA (polymethyl methacrylate) having a thickness of about 50 nm is formed on the silicon layer 13 of the SOI substrate composed of the silicon layer 13 (thickness of about 500 nm) and the silicon layer 13 (thickness of about 50 nm). Applied. Next, the pattern shape was exposed by a point electron beam, and this was subsequently developed to form a resist pattern 14 having a space portion as shown in FIG. Next, FIG.
As shown in FIG. _{2, an} SiO ₂ film 15 was deposited on the resist pattern 14 by sputtering to a thickness of about 50 nm. Thus, the SiO ₂ film 15a was simultaneously deposited on the silicon layer 13 in the space of the resist pattern 14.

Next, the resist pattern 14 was removed by lift-off, and the SiO ₂ film 15 deposited on the resist pattern 14 was also removed. Here, the SiO ₂ film 15a serving as a mask was left without being removed. Then, using the SiO ₂ film 15a as a mask, the silicon layer 13 was etched by wet etching or dry etching to leave the silicon layer only under the SiO ₂ film 15a as shown in FIG. This remaining silicon layer
The quantum junction 3 is formed by forming the electrodes 1, 2 and the quantum structure 3 close to the electrode 2. Alternatively, a tunnel junction in which the quantum structure is bonded to the electrode may be formed by changing the pattern shape of the resist. The above-described embodiment is an example. If the purpose of forming a tunnel junction having an electrode in which the structure is controlled and the distribution of the wave function has energy dependence is achieved, the method and material for forming the tunnel junction are as follows. It is not limited to this.

In addition, in the above embodiment, electron beam exposure was used as a patterning method, but any appropriate method can be used, for example, an excimer laser,
An X-ray laser or photolithography using synchrotron radiation as a light source may be used.

Further, since the present invention is not limited to Si-based, mixed crystal compound semiconductors such as aluminum gallium arsenide, which can be used for MBE and vapor phase growth, and metals and metal oxides such as aluminum. Is also applicable, and does not limit the material system such as a microstructure by self-organization.

[0059]

In the electronic device according to the present invention, the tunnel resistance and the junction capacitance can be independently designed without being limited by the material, so that the operating temperature can be increased while maintaining the required operating speed. Will be possible. Or, conversely, it is possible to improve the operation speed while maintaining the required operation temperature. Further, the electronic device of the present invention can be applied to a single electronic device. More specifically, a single-electron element capable of tunneling electrons only in a specific direction depending on the directionality of a tunnel, and a single-electron element capable of suppressing multiple tunneling, are limited in material only by controlling the structure and the like. It can be realized without. Since the electronic device according to the present invention is not limited to materials, it can be applied to silicon-based devices. Therefore, the typical silicon element M
It can be applied to a mixed circuit of an OS device and a single electron element,
It is possible to realize a device with extremely low power consumption.

[Brief description of the drawings]

FIG. 1 is a schematic perspective view showing a structure of an electronic device according to an embodiment of the present invention.

FIG. 2 is a diagram illustrating an electronic device of the present invention when no voltage is applied. (a) is an energy level diagram showing coupling of wave functions, (b) is an energy band diagram, and (c) is a schematic diagram showing an equivalent circuit.

FIG. 3 is a diagram illustrating an electronic device of the present invention when a voltage V (eV <E ₀ ) is applied. (a) is an energy band diagram, (b) is a schematic diagram showing an equivalent circuit.

FIG. 4 is a diagram illustrating an electronic device of the present invention when a voltage −V (eV <E ₀ ) is applied. (a) is an energy band diagram, (b) is a schematic diagram showing an equivalent circuit.

FIG. 5 is a diagram illustrating an electronic device of the present invention when a voltage V (eV> E ₀ ) is applied. (a) is an energy band diagram, (b) is a schematic diagram showing an equivalent circuit.

FIG. 6 is a diagram illustrating an electronic device of the present invention when a voltage −V (where eV> E ₀ ) is applied. (a) is an energy band diagram, (b) is a schematic diagram showing an equivalent circuit.

FIG. 7 is a schematic diagram showing a tunnel resistance of an electronic device according to another embodiment of the present invention.

FIG. 8 is a diagram illustrating an electronic device according to another embodiment of the present invention. (a) is a schematic perspective view showing a structure, (b) is a spatial view of an energy band, and (c) is a plan view of the energy band.

FIG. 9 is a schematic diagram showing a tunnel junction and its directionality.

FIG. 10 is a diagram illustrating a single-electron element according to another embodiment of the present invention. (a) is an energy band diagram, (b) is a schematic diagram showing an equivalent circuit.

FIG. 11 is a diagram illustrating a multiple-tunneling suppressing single-electron element according to another embodiment of the present invention. (a) is an energy band diagram in an operation region, (b) is an energy band diagram in a Coulomb blockade region, and (c) is a schematic diagram showing an equivalent circuit.

FIG. 12 is a perspective view illustrating a method for forming an electronic element of the present invention.

FIG. 13 is a schematic diagram illustrating a tunnel resistance of an electronic device using a conventional tunnel junction.

FIG. 14 is a diagram illustrating an electronic device using a conventional tunnel junction. (a) is an energy band diagram in an operation region, and (b) is a schematic diagram showing an energy band in a Coulomb blockade region.

[Explanation of symbols]

1, 2 electrode 3 quantum structure 11 silicon substrate 12 buried oxide film 13 silicon layer 14 resist pattern 15 SiO ₂ film 15a mask (SiO ₂ film)

Claims (5)

[Claims] 1. An electronic device comprising: at least one pair of electrodes; a tunnel junction formed at the electrode; and means for imparting energy dependence to a distribution of a wave function at the electrode, wherein the tunnel junction of the tunnel junction is provided. An electronic device in which a resistance changes depending on a voltage applied to the electrode, whereby a capacitance component and a tunnel component of the electrode are independently set, and the tunnel junction has directionality. 2. The method according to claim 1, wherein the means for imparting energy dependence to the distribution of the wave function is one or more quantum structures disposed in close proximity to one of the pair of electrodes. Item 2. The electronic element according to Item 1. 3. The method according to claim 2, wherein the means for imparting energy dependence to the distribution of the wave function is one or more quantum structures arranged in contact with one of the pair of electrodes. Item 2. The electronic element according to Item 1. 4. The electronic device according to claim 1, wherein the electronic device is a single electronic device. 5. At least one pair of said tunnel junctions, comprising a Coulomb island between said pair of tunnel junctions, coupled in series such that said directions of said pair of tunnel junctions are opposite to each other, The electronic device according to claim 4, which suppresses multiple tunneling.